Head mounted display (HMD) devices and other near-eye display systems utilize a display panel mounted in front of a user's eyes to display various types of content, including virtual reality (VR) content, augmented reality (AR) content, and the like. Eye tracking often is implemented in such near-eye display systems to facilitate various functionalities, such as foveated imaging (also known as gaze-contingent imaging), eye-movement based user input or interaction, and the like. Conventional eye tracking mechanisms typically employ a complex arrangement of lenses and mirrors to capture an image of the eye, and from this image estimate a gaze direction of the eye. However, the complex optical mechanism required in conventional systems to provide this eye tracking function without occluding the display panel often inhibits implementation of a small form factor for the HMD device.